Broad band near-infrared emitting phosphors activated with Cr 3+ ions have great potential in a variety of applications. The luminescence efficiency and thermal stability are two critical parameters that are highly concerned in practical applications. In this work, a series of Cr 3+ ion-activated Ca 9 Ga(PO 4 ) x (VO 4 ) 7-x were synthesized. The photoluminescence (PL) properties of Cr 3+ were studied as functions of coordination environment, Cr 3+ concentration and temperature. The coordination environment of Cr 3+ ions is modified by gradually substitution of P by V without change the crystal structure of the host lattice. A continuous solid solution is formed, and the cell parameters and volume increase monotonically with V content. Great improvement in the intensity is observed for Ca 9 Ga(PO 4 ) 3.5 (VO 4 ) 3.5 , which increases by 26 and 2.4 times than the parents compositions Ca 9 Ga(PO 4 ) 7 and Ca 9 Ga(VO 4 ) 7 , respectively. Decay dynamic analysis suggests that both coordination environment modification and reduction of quenching center responsible for the great enhancement. An optimized concentration of 3.0 % is revealed and the intensity at 433 K maintains 81.1 % of the intensity at 293 K, respectively.
Yuanzheng Zhang,Xiang Chen,Chao Liang,Lifeng Yin,Yang Yang
This study develops an advanced single-atomic iron-loaded graphitic carbon nitride (Fe 1 /CN) with unparalleled efficiency for converting peroxymonosulfate (PMS) to oxidants for water treatment. We found that acid-etching of Fe 1 /CN leads to the reconstruction of conventional Fe 1 –N 4 to Fe 1 –C 2 N 1 active sites. The acid-induced Fe 1 –C 2 N 1 sites are more favorable for PMS binding and have a lower energy barrier for 1 O 2 production. The precise tuning of the coordination environment bestows the acid-etched Fe 1 /CN with 29 times higher rate constants of bisphenol A degradation than its pristine counterparts. Further, the particulate catalysts were assembled into a self-supported catalytic membrane, which demonstrates excellent long-term durability throughout 170 h flow-through tests in both synthetic and real wastewater . This work provides pivotal insights into improving PMS activation activity by regulating the coordination environment around single atomic Fe sites. The engineering innovation laid the groundwork for new point-of-use water treatment devices.
A novel synthetic strategy is proposed to create high zero-valent platinum (Pt) components, sub-nanometer Pt clusters, and three-dimensional (3D) Pt/ nitrogen-doped MXene (N-Ti 3 C 2 T x ) catalyst through electrostatic self-assembly combined with non-in-situ doping pyrolysis. Compared with the primary Pt/Ti 3 C 2 T x , the N-doped Pt/N-Ti 3 C 2 T x , which has a 3D wrinkled porous structure, increases the residence time of methylcyclohexane (MCH) on the catalyst surface during gas–solid reactions and improves the mass transfer efficiency of MCH. In addition, the N-doped Pt/N-Ti 3 C 2 T x , which optimizes the electronic coordination environment, produces sub-nanometer Pt clusters, in which Pt mainly exists as Pt (0) (80.78 %) and avoids the presence of low catalytic activity Pt (IV). The Pt 0.5% /N-MXene catalyst exhibits significant catalytic performance in the dehydrogenation of MCH in a fixed-bed reactor, with a hydrogen evolution rate of 636.30 mmol·g Pt -1 ·min - 1 , which significantly surpasses 176.60 mmol·g Pt -1 ·min - 1 for N-undoped Pt 1% /MXene and 78.13 mmol·g Pt -1 ·min - 1 for commercial Pt 1% /TiO 2 . Density functional theory calculations, Pt/N-Ti 3 C 2 T x exhibits lower Pt electronic states and has a d -band center closer to the Fermi level than Pt/Ti 3 C 2 T x . This configuration leads to the stronger MCH adsorption on the Pt sites of Pt/N-Ti 3 C 2 T x , promoting faster H 2 generation and release, thereby achieving a higher catalytic activity.
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